The present invention relates to a system and method for minimizing torque disturbances cause by changes in engine operation such as when regenerating a diesel particulate filter (DPF).
Diesel engines typically use a particulate filter to minimize the emission of such particles. The stored particles can be periodically purged, or burned, by raising the filter to a predetermined temperature. In diesel engines, however, during low load operation the exhaust gas temperature may not be high enough to start the regeneration process.
Various methods have been proposed for created such regeneration, such as throttling the engine. The inventors herein have recognized, however, that even with such methods, exhaust temperatures may not be high enough to start regeneration. Further, even with these measures, it may take a relatively long time to start the regeneration.
The above disadvantages are overcome with a method for controlling output of a vehicle powertrain having an engine coupled to a particulate filter and a torque transmitting unit with multiple transmission paths including multiple clutches, the vehicle also having an electronic control unit. The method comprises: determining whether particulate filter regeneration should be commenced; increasing engine output torque based on said determination to raise exhaust gas temperature; and during said increased engine output, transmitting torque through said torque transmitting unit via at least two paths, and adjusting a clutch parameter of at least one of the clutches of said torque transmitting unit.
By adjusting a clutch parameter, for example, clutch hydraulic pressure, it is possible to transmit torque through multiple paths of the transmission in such a way that the increase in input torque causes substantially no change in the output torque. In other words, by changing the pressure, and thus the transmitted torque, in response to the torque disturbance changes the way in which torque is transmitted through the unit, and thus changes the net output torque. Further, by increasing engine output torque, it is possible to more rapidly start particulate filter regeneration.
Note that such an approach can be utilized in combination with other methods that raise exhaust gas temperature.
The above advantages, other advantages, and other features of the present invention will be readily apparent from the following detailed description of the invention and the following drawings, taken alone or in combination.